The present invention relates to a piping structure of a working machine. More specifically, the invention relates to a piping structure of a working machine, in which a swivel joint that is a rotary joint for fluid is provided at a coupling portion where a pair of members of a working machine are swingably coupled together via a shaft.
Referring to FIG. 7, various working devices, such as a working device 52 equipped with a quick coupler 51, is swingably attached to an end of an arm 50 of a hydraulic shovel which is a typical working machine, by using a shaft 54. By a swing operation link 53 provided for the arm 50, the working device 52 swings between a lower position shown by a solid line and an upper position shown by a two-dot chain line. The working device 52 is provided with a hydraulic cylinder 51a that is a fluid pressure actuator, and the hydraulic cylinder 51a and an arm 50 are coupled together through a hydraulic piping 56. A flexible hydraulic hose 56a is used for the hydraulic piping 56 in the coupling portion so as to be able to follow the swinging working of the working device 52, one end thereof being connected to a piping 56b fixed to the arm 50 and the other end thereof being connected to the hydraulic cylinder 51a of the working device 52. The illustrated hydraulic cylinder 51a is of the double-acting type, and a total of two pipings 56 are provided, one on the head side H and the other one on the rod side R.
The piping structure of the conventional working machine of the above-mentioned construction, however, involves problems as described below.
That is, when the working device 52 swings at an end of the arm 50, the hose 56a bends between a xe2x80x9cstretched state (indicated by a solid line)xe2x80x9d in which both ends thereof are separated away from each other and a xe2x80x9cslackened state (indicated by a two-dot chain line)xe2x80x9d in which both ends thereof are brought close to each other due to the swinging motion of the working device 52. When bent, the hose 56a is liable to come in contact with the arm 50 or the working device 52. In the xe2x80x9cslackened statexe2x80x9d in particular, the hose 56a hangs down between the arm 50 and the working device 52 or extends over a side portion of the arm 50, often being caught between the arm 50 and the working device 52 or coming in contact with the surrounding obstacles. Consequently, the life of the hose is shortened or the hose is damaged.
The present invention has been made in view of the above-mentioned fact, and its technical assignment is to provide a piping structure of a working machine, which makes it possible to prevent the piping at a coupling portion where a pair of members are swingably coupled together via a shaft, from being damaged.
In the present invention, as a piping structure of a working machine to solve the above-mentioned technical assignment, there is provided a piping structure of a working machine, comprising a swivel joint which is a rotary joint for fluid and is disposed, on the outer side in the radial direction of a shaft of a coupling portion where a pair of members are swingably coupled together via said shaft, so as to swing on the axis of swinging motion as a center of rotation.
In the piping structure of the working machine according to the present invention, a swivel joint is provided at the coupling portion where the pair of members are swingably coupled together. Therefore, since the piping between the pair of members is arranged via the swivel joint, it does not need to use the flexible piping such as the hose.
In a preferred embodiment, the swivel joint comprises a cylindrical stator mounted on either one of said pair of members and a rotor rotatably fitted to the outer periphery of the stator.
The swivel joint is constituted by a stator and a rotor arranged on the outer side of the shaft that couples the pair of members.
According to a preferred embodiment, further, a cylindrical boss to which the stator is fitted is provided between the stator and the shaft, the boss being attached to either one of said pair of members.
The mounting of the swivel joint on the coupling portion is guided by the boss. Further, a thrust force acting on the pair of members in the axial direction is received by the boss, so that an excessive large force will not act on the swivel joint.
In a preferred embodiment, the pair of members are an arm equipped with the working machine and a working device swingably coupled to the arm.
The piping between the arm of the working machine and the working device coupled to the arm is prevented from being damaged.